Reciprocating piston engine with rhombic drive and even power intervals



July 14, 1970 KLAUDER, JR 3,520,285

RECIPROCATING PISTON ENGINE WITH RHOMBIC DRIVE AND EVEN POWER INTERVALS Filed Nov. 13, 1968 2 Sheets-Sheet l V i 1 2 e i i h ATTORNEY y 14, 1979 T. KLAUDER, JR 3,520,285

RECIPROCATING PISTON ENGINE WITH RHOMBIC DRIVE AND EVEN POWER INTERVALS Filed NOV. 13, 1968 2, Sheets-Sheet 2 all 72 I INVENTOR.

6 BY 01125 K/azzazgj:

ATTORNEY United States Patent 3,520,285 RECIPROCATING PISTON ENGINE WITH RHOMBIC DRIVE AND EVEN POWER INTERVALS Louis T. Klauder, Jr., Birmingham, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Nov. 13, 1968, Ser. No. 775,467 Int. Cl. F02b 75/24 U.S. Cl. 123-56 14 Claims ABSTRACT OF THE DISCLOSURE Several embodiments of reciprocating piston engines having an even number of cylinders arranged in two opposed banks, the pistons thereof being connected to two oppositely rotating crankshafts by rhombic drive means. The engines have a minimum of four cylinders with the various components arranged to provide relationships between the engine operating cycle, the total number of cylinders and the phase lag between the pistons of opposed cylinders such that equal intervals of crankshaft rotation are provided between sequentially spaced power strokes of the various engine cylinders.

FIELD OF THE INVENTION This invention relates to reciprocating piston engines and, more particularly, to engines having horizontally opposed cylinders and dual crankshafts wherein the pistons of opposite cylinders are interconnected by rhombic drive means and the various engine components are arranged to obtain equal intervals between sequentially spaced power impulses of the various cylinders.

DESCRIPTION OF THE PRIOR ART U.S. Pat. No. 613,769 granted Nov. 8, 1898, to W. F. Lanchester, and the disclosure of which is hereby incorporated by reference into this application, illustrates certain embodiments of two-cylinder horizontally opposed engines utilizing dual crankshafts and rhombic drive means interconnecting the pistons and crankshafts. Objects of the Lanchester construction were to eliminate the torque reaction present in the frame of conventional engines by the use of the dual oppositely rotating crankshafts and to permit complete balance of the rotating and reciprocating components by the use of counterweights carried on the crankshafts. While it is known that such engines were actually manufactured to some extent around the turn of the century, they are not in common use today, presumably due to their increased complexity over more conventional engine structures.

There are, however, believed to be applications for engines wherein the added complexity of the rhombic drive construction would be justified in order to obtain freedom from some of the structure-borne vibrations caused by the torque reactions and bending stresses applied to the cylinder blocks of conventional engines. Such freedom would appear especially advantageous in respect to diesel and other high compression engines where the firing pressures and instantaneous torques are relatively high but could also be used to advantage in other internal combustion engines as well as external combustion engines such as steam and hot gas types.

The patented Lanchester engine has, however, one shortcoming which is avoided by most current multi-cyl inder engines, that being that the intervals between the power strokes of the two opposite cylinders are uneven, resulting in excessive torsional vibrations which must be overcome either by large flywheels or resilient drive couplings. Thus the prior art two-cylinder Lanchester engine 3,520,285 Patented July 14, 1970 ice SUMMARY OF THE INVENTION The present invention proposes arrangements by which the rhombic drive construction of Lanchester may be applied to opposed cylinder engines of four cylinders or more in a manner so as to obtain the desired result of even intervals between the power impulses of the cylinders, thus combining the advantages of the Lanchester design with those of present day multi-cylinder engines while eliminating some of the disadvantages of each.

This result is accomplished by properly selecting the relative positions of the crankshafts and pistons and the relative dimensions of their connecting structure so as to obtain an appropriate angular phase lag between the pistons of opposed cylinders which is equal to or a multiple of the angular interval between sequential power impulses of the cylinders. The manner in which this may be done, as well as various factors which might affect the practicality of the resulting arrangements in certain instances, are discussed in the following description of certain preferred embodiments of the invention taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, FIG. 1 is a cross-sectional view of an engine formed according to the invention and showing one of its pairs of oppositely disposed cylinders.

FIG. 2 is a diagram indicating certain relationships between the components of engines formed according to the invention.

FIGS. 3 and 4 are schematic plan and end views respectively of a six-cylinder engine formed according to the invention and having a phase lag between the pistons of the opposite cylinders.

FIGS. 5 and 6 are schematic plan and end views re spectively of an eight-cylinder, two-stroke cycle engine formed according to the invention with a phase lag between the pistons of the opposite cylinders.

FIGS. 7 and 8 are schematic plan and end views re spectively of a ten-cylinder, two-stroke cycle engine formed according to the invention and having a 108 phase lag between the pistons of the opposite cylinders.

FIGS. 9 and 10 are schematic plan and end views respectively of another ten-cylinder engine formed according to the invention but having a 144 phase lag between the pistons of the opposite cylinders.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1 of the drawings, numeral 12 generally indicates a diesel type internal combustion engine having a cylinder block 14 which includes a pair of generally opposed cylinder banks 16 and 18 respectively. Within each cylinder bank is a plurality of longitudinally spaced cylinders 20 having their axes in a common plane and arranged in generally oppositely disposed pairs. The opposed pairs of cylinders are preferably coaxial but may be slightly offset longitudinally from one another to provide for the use of side-by-side connecting rods.

Within each of the cylinders is a piston 22 arranged to reciprocate therein and form therewith a conventional variable volume combustion chamber. Means, including injectors 24, are provided to supply fuel to the combustion chambers and conventional valve means, not shown, are provided to permit the introduction of air and the exhaust of combustion products from the combustion chambers in a conventional manner.

Centrally disposed between the opposed cylinders and arranged for opposite rotation on axes equally spaced on opposite sides of and parallel to the plane of the cylinders are first and second crankshafts 26 and 28. Each of the crankshafts includes a plurality of throws 30, including one throw for each pair of cylinders. Connecting rods 32 and 34 are provided to connect each crankshaft throw 30 with both the pistons 22 of its associated pair of cylinders so that each piston of the engine is connected to both crankshafts and each crankshaft throw is connected with two pistons. Balance weights 35 are provided at suitable locations on the crankshafts to balance the rotating and reciprocating engine parts. Such weights may be located at each pair of cylinders or arranged in any other suitable manner consistent with the engine cylinder and crankshaft arrangement. Suitable covers 36 and 38 are provided to enclose the crankshafts and connecting rods of the engine.

A number of arrangements for connecting the crankshafts and pistons are possible of utilization including those shown in the various figures of the previously mentioned Lanchester Pat. No. 613,769. In addition, it is possible to use a fork and blade construction to connect two connecting rods to a piston so that both rods may act along lines intersecting the piston axis. This type of construction may also be used in connecting the rods to the crankshaft as is shown in FIG. 3 of the aforementioned Lanchester patent. Alternatively, it is possible to use more conventional side-by-side rods at the crankshaft connection by longitudinally offsetting the axes of the opposite cylinders slightly. However, the use of side-by-side rods at the piston connection is not believed practical, although it might be possible, since such an arrangement there would create twisting forces on the piston which would have to be taken up by the connecting rod bearings.

FIG. 2 illustrates diagrammatically certain relationships of rhombic drive engines of the type disclosed in FIG. 1. In the figure, numeral 40 indicates the axis of one of the engine crankshafts which has a throw 42 positioned at radius r from the crankshaft axis. A connecting rod 43 of length l connects throw 42 with one of the engine pistons at point 44. This point is moveable along the axis of its cylinder through a distance s equal to the piston stroke. It represents the distance between the plane 46 formed by the axes of all the cylinders and the axis 40 of the crankshaft.

The angle is the angle formed between a perpendicular 47 to the plane 46 of the cylinders and the connecting rod 43 at the outer dead center position of the piston. This angle equals one-half of the so-called phase lag between the opposed pairs of pistons, the phase lag being defined as the smallest angle through which the crankshaft turns between the outer dead center positions of the opposite pistons. The angle 95 represents the angle formed between the connecting rod 43 and a perpendicular to the plane of the cylinders when the piston is at its inner dead center position. The angle represents the smallest angle which the connecting rod 43 makes with a perpendicular to the plane of the cylinders.

It should be apparent that the various angles and dimensions are interdependent to a great extent and are subject to various practical limitations which would exist in the construction of an actual engine. One such limitation is that the angle 0 must not be too small in order that the forces on the connecting rods and journals do not become excessive. A minimum angle 1/ of about 30 is believed to be a reasonable, practical limit. The dimension hr must be sufficiently large to provide clearance so that the ends of the connecting rods connected to the two crankshafts will not strike one another. In addition, reasonable limitations as to the radius r of the crankshaft throw and length l of the connecting rod in relation to the piston stroke s must be preserved.

With the foregoing relationships established, the relative size of the engine may be stated generally in relation to its dimensional characteristics. For example, an indica 4 tion of the height of the engine is given by the quantity H=2(h+r) while the width is generally indicated by the quantity W=2(l+r) sin 0.

It should be noted that the engine dimensions determine the phase lag between the pistons of opposed cylinders which is equal to the angle 20. The phase lag, in conjunction with the operating cycle and selected firing order of the engine, determines the angular interval between the power strokes of the opposite pistons. This being the case, it is necessary, in order to obtain equal firing intervals between cylinders, that the phase lag selected bears a particular relationship to the number of engine cylinders and the engine operating cycle.

In a two-stroke cycle (or two cycle) engine, in which the cylinders all fire within one complete rotation of the crankshaft, the firing interval will normally equal 360 of crankshaft rotation divided by the number of cylinders. To obtain even firing intervals, then, the phase lag chosen for such an engine must equal the angular firing interval or be a multiple of it. In the same manner, the normal firing interval of a four-stroke cycle (or four cycle) engine, in which all of the cylinders fire in two crankshaft revolutions, is equal to 720 of crankshaft rotation divided by the number of cylinders. In such an engine, even firing intervals are obtainable only if the phase lag is equal to or a multiple of this firing interval. Table I indicates the possible phase lags which will give even firing intervals in a number of engine types.

TABLE I.PI-IASE LAGS FOR EVEN FIRING INTERVALS Firing intervals Strokes per cycle No. of cylinders (deg) Phase lag (deg) 1 Dual. 2 Impossible.

Reference to FIG. 2 illustrates that, unless a more complicated linkage is used between pistons and crankshafts, the phase lag must be something less than 180 in order to provide for separation of the crankshafts. In addition, a phase lag of less than about 90 is not practical due to limitations of the piston stroke by the 30 minimum limit for the angle ,0 of the connecting rod near its inner dead center position. Due to firing order limitations caused by engine geometry, a number of phase lag figures which might otherwise be possible cannot be worked out so as to permit equal spacing between firings of the cylinders of the various engine arrangements.

The notation dual in the firing interval column of Table I is intended to indicate that the engine cylinders are to be fired two at a time with equal firing intervals existing only between the sequentially fired cylinders. This permits the use of normal four cycle engine arrangements in two cycle engines but would only be chosen where advantageous dimensional characteristics are obtained as will be subsequently noted.

In most such cases, the arrangement will provide for equal firing intervals between the cylinders of each bank with the cylinders to be fired at the same time being located in opposite banks. There are exceptions, however. For example, an eight-cylinder engine could be arranged as if it were two four-cylinder engines or a twelvecylinder engine could be arranged as if it were two sixcylinder engines with the corresponding cylinders of each half-engine firing at the same time In such cases, the cylinders firing together would be in the same bank and the separate crank throws of these cylinders would be aligned.

It should also be noted that while the subsequently described embodiments disclose crankshaft arrangements in which the crank throws are radially spaced at equal angular intervals, this is not an essential qualification since, in some instances, equal firing intervals may be obtained with other crank throw arrangements.

Using the above information, it is possible to calculate the relative proportions of engines having the above characteristics by using reasonable limiting assumptions. Table II below indicates such relative dimensions using an assumed stroke s of 3.0 and a limitation of the quantity hr of about 1.33. The minimum angle 1,0 of 30 is used where possible but is increased where necessary to avoid reducing hr below its limit. With these assumptions, the values of Table II were determined.

TABLE II.-RELATIVE ENGINE PROPORTIONS Phase lag (d g) il (deg) 1 Z h with 90 phase lag is considerably greater than that of the others listed and, thus, it appears that in most instances the use of a 90 phase lag would not be practical.

The most practical engines utilizing rhombic drive and having even firing intervals are thus seen to be those having phase lags of 108, 120, 135 and 144. Such engines are illustrated in FIGS. 3 through 10.

FIGS. 3 and 4 show one possible arrangement of a six-cylinder engine intended primarily for four cycle operation and having a 120 phase lag between the opposite pistons. The six cylinders are arranged in two opposed banks, the cylinders of one of the banks being identified as 1a, 2a, and 3a and being coaxially arranged in opposed pairs with the respective cylinders of the opposite bank designated 1b, 2b, and 3b. Each of the cylinders has reciprocably disposed within it a piston 48.

Intermediate the banks of cylinders and spaced equidistantly on opposite sides of the plane of the cylinders are a pair of crankshafts 50, 52 each having three throws angularly spaced at equal intervals of 120. The crankshafts are arranged for opposite rotation and have their throws located in proper phase so that the opposed pistons of each bank may be connected to one of the throws of each crankshaft by means of fork and blade connecting rods 54, 56 respectively. The relative dimensions and positions of the various components are selected such that, upon rotation of the crankshafts, the opposed pairs of pistons reciprocate with a phase lag of 120 between their outer dead center positions. With this arrangement, the selection of a proper firing order will result in equally spaced intervals of 120 between the sequential firing impulses of the various cylinders. More than one possible firing order may be selected. For example, if it is desired to alternately fire the cylinders of opposite banks, the firing order would be 1a, 1b, 3a, 3b, 2a, and 2b. However, the cylinders of one bank could be fired followed by the cylinders of the other, yielding the firing order 1a, 2a, 3a, 3b, 1b, and 2b. These firing orders could, of course, be changed by rotation of the crankshafts in an opposite direction or by rearrangement of the crankshaft throw positions still, however, using the 120 spacing. Such changes would not alter the basic characteristics of the engine.

It is of interest to note that, while an arrangement of six-cylinder, two cycle engine to have all cylinders firing sequentially with evenly spaced intervals would require a phase lag of 180, a six-cylinder engine arranged in the manner of FIGS. 3 and 4 could be operated with evenly spaced firing intervals on the two-stroke cycle with a phase lag by firing two cylinders, one in each bank, at the same time and spacing firings of the cylinders of the same bank at 120 intervals. In this way, a practical configuration for a six-cylinder, two cycle engine may be obtained for possible use in certain applications.

FIGS. 5 and 6 illustrate an arrangement for an eightcylinder, two cycle engine having a phase lag of between opposed pistons. Two opposed banks of four cylinders each are provided, the cylinders of one bank being identified as 1c, 2c, 3c and 40, while the respective opposite cylinders of the other bank are designated 1d, 2d, 3d and 4d. As before, the cylinders receive pistons 54 connected by fork and blade connecting rods 56 and 58 respectively to the throws of a pair of crankshafts 60, 62 having each four throws angularly spaced at equal intervals of 90. The aligned throws of each crankshaft are connected to both pistons of an associated pair of opposed cylinders. The arrangement of the engine components to provide a 135 phase lag between the pistons of opposed cylinders requires a particular firing order, dependent upon the relative positions of the various crank throws which may be arranged as desired.

In FIGS. 7 and 8, a ten-cylinder, two cycle engine arrangement is illustrated in which the phase lag is 108. In this arrangement, the cylinders are located five in each opposed bank, those of one bank being identified as 1e-5e, while the respective opposed cylinders of the opposite bank are designated lf-Sf. The engine includes two spaced crankshafts 64, 66, each of which has five longitudinally spaced throws which are also angularly spaced at 72 intervals and are each associated with a different pair of opposed cylinders. Fork and blade connecting rods 68 and 70 are utilized to connect the crankshaft throws with the pistons 72 of the cylinders. The arrangement of the components to provide a 108 phase lag between opposite pistons also requires a specific firing order depending upon the particular arrangement of the crankshaft throws, which may be selected as desired.

In FIGS. 9 and 10, a different ten-cylinder engine arrangement is shown, primarily intended for use as a four cycle engine and having a phase lag between opposite pistons of 144". Like the arrangement of FIGS. 7 and 8, the cylinders are arranged in two opposed banks of five each, the aligned cylinders of one bank being designated lg-Sg with the respective opposed cylinders of the opposite bank being identified as 111-511. The arrangement includes two crankshafts 74, 76 like those of the arrangement of FIGS. 7 and 8, in that they each include five throws equally spaced angularly at 72 intervals and axially spaced in alignment with their respective pairs of opposed cylinders. Pistons 78 in each of the cylinders are connected through fork and blade connecting rods 80 and 82 respectively with their respective crankshaft throws as in the previously described arrangements. The dilference, then, between the arrange ment of FIGS. 9 and 10 and that of FIGS. 7 and 8 is in the positioning of the parts to provide a phase lag of 144 which is particularly suitable for the intended operation of the engine on the four-stroke cycle with even firing intervals between the cylinders. As in the case of the other four cycle arrangements of Table I, the ten-cylinder engine of FIGS. 9 and 10 may be operated with various selections of firing orders dependent both upon the choice of whether to alternate firing between the banks of cylinders or to fire those of one bank and then those of the other and upon the relative positioning of the crankshaft throws which may be selected as deired.

In addition, the engine arrangement of FIGS. 9 and 10 may, like the other four cycle arrangements, be utilized for operation on the two-stroke cycle by providing for two cylinders, one in each bank, to fire at the same time and arranging a firing order with equal intervals of 72 between the firing impulses of the cylinders of each bank. Such an arrangement might be desirable as opposed to the arrangement of FIGS. 7 and 8 if it were especially important that the engine have a low height. However, as in all such dual firing arrangements, the torque impulses would not be as smooth since the firing impulses would be spaced at twice the interval and be twice as great as would those of an individual firing two cycle arrangement such as that of FIGS. 7 and 8.

While the invention has been disclosed by reference to certain specific embodiments of engines, one of which is indicated as being of the diesel type, it should be understood that the invention is equally applicable to other reciprocating piston engines of both the internal and external combustion types. Furthermore, the description of various specific embodiments and modifications thereof which may be utilized in the practice of the inventive concept disclosed herein should not be taken as intending to limit the practice of the invention to the specific arrangements mentioned, as it is realized that numerous other engine arrangements may be provided which might include the concepts taught herein with respect to the use of multiple cylinder engines utilizing rhombic drives and arranged to provide equal firing intervals. It is accordingly desired that the invention be given the full scope permitted by the language of the following claims.

I claim: 1. A fluid pressure engine comprising an even number of cylinders arranged in two opposed co-planar banks of at least two cylinders each, the cylinders of the opposed banks being arranged in generally opposed pairs,

a piston reciprocably moveable in each of the cylinders, a pair of oppositely rotatable crankshafts centrally disposed on axes intermediate the cylinder banks and spaced equidistant from and on opposite sides of the plane of the cylinders, said crankshafts each having one crank throw for each pair of opposed cylinders and connecting rods connecting each of the pistons with their respective crank throws of both crankshafts and the arrangement of the parts being such that equal intervals of crankshaft rotation are provided between sequentially spaced power strokes of the pistons of the various engine cylinders.

2. The engine of claim 1 wherein the cylinders of said generally opposed pairs of cylinders are coaxially arranged.

3. The engine of claim 1 wherein the parts are arranged such that the power strokes of the pistons of all the engine cylinders occur sequentially at equally spaced intervals of crankshaft rotation.

4. The engine of claim 1 wherein the parts are arranged such that the power strokes of the pistons of each bank of cylinders occur sequentially at equally spaced intervals of crankshaft rotation while the power strokes of each piston of one bank of cylinders occur at the same time as the power strokes of a correspondingly timed piston of the opposite bank of cylinders.

5. An internal combustion engine comprising a pair of opposed co-planar banks of cylinders, said banks having at least two cylinders each, with the cylinders of the opposite banks being arranged in generally opposed pairs,

a piston reciprocably disposed in each of the cylinders,

two crankshafts disposed intermediate the cylinder banks and oppositely rotatable on axes spaced oppositely and equidistantly from the plane of the cylinders, said crankshafts each having one crank throw for each pair of cylinders,

connecting rods connecting each of the pistons with their respective crank throws of both crankshafts and balancing means arranged to substantially balance the reciprocating and rotating parts,

the arrangement of various parts being such as to relate the engine operating cycle, the total number of cylinders and the phase lag between the movements of the pistons of opposed cylinders so that equal intervals of crankshaft rotation are provided between sequentially spaced power strokes of the pistons of the various engine cylinders.

6. An internal combustion engine as defined in claim 5 wherein the cylinders of said generally opposed pairs of cylinders are coaxially arranged.

7. An internal combustion engine as defined in claim 5 wherein the parts are arranged such that the power strokes of the pistons of all the engine cylinders occur sequentially at equally spaced intervals of crankshaft rotation.

8. The engine of claim 7 wherein said engine is arranged to operate on a four-stroke cycle and includes a total number of cylinders equaling a multiple of six, the phase lag between the movements of the pistons of op posed cylinders being of crankshaft rotation.

9. The engine of claim 7 wherein said engine is arranged to operate on a two-stroke cycle and includes a total number of cylinders equaling a multiple of eight, the phase lag between the movements of the pistons of opposed cylinders being of crankshaft rotation.

10. The engine of claim 7 wherein said engine is arranged to operate on a four-stroke cycle and includes a total number of cylinders equaling a multiple of ten, the phase lag between the movements of the pistons of opposed cylinders being 144 of crankshaft rotation.

11. The engine of claim 7 wherein said engine is arranged to operate on a two-stroke cycle and includes a total number of cylinders equaling a multiple of ten, the phase lag between the movements of the pistons of opposed cylinders being 108" of crankshaft rotation.

12. An internal combustion engine as defined in claim 5 wherein the parts are arranged such that the power strokes of the pistons of each bank of cylinders occurs sequentially at equally spaced intervals of crankshaft rotation while the power strokes of each piston of one cylinder bank occur at the same time as the power strokes of a correspondingly timed piston of the opposite bank.

13. The engine of claim 12 wherein said engine is arranged to operate on a two-stroke cycle and includes a total number of cylinders equaling a multiple of six, the .phase lag between the movement of the pistons of opposed cylinders being 120 of crankshaft rotation.

14. The engine of claim 12 wherein said engine is arranged to operate on a two-stroke cycle and includes a total number of cylinders equaling a multiple of ten, the phase lag between the movement of the pistons of opposed cylinders being 144 of crankshaft rotation.

References Cited UNITED STATES PATENTS 613,769 11/1898 Lanchester. 874,200 12/ 1907 Hoyt. 1,698,598 1/1929 Kussner.

FOREIGN PATENTS 85,514 2/1936 Sweden.

WENDELL E. BURNS, Primary Examiner US. 01. X.R. 123 192, 197 

